WO2009083165A1

WO2009083165A1 - Chassis plastic component for a motor vehicle, and the use thereof

Info

Publication number: WO2009083165A1
Application number: PCT/EP2008/010815
Authority: WO
Inventors: Ernst Opel; Rainer Goller; Gerhard Lebisch
Original assignee: Rehau Ag + Co
Priority date: 2007-12-21
Filing date: 2008-12-18
Publication date: 2009-07-09
Also published as: DE102007062945A1

Abstract

The invention relates to a chassis plastic component (3) for a motor vehicle, comprising a carrier body (7) having a base body (8) made of plastic. Paint (9) may be applied on the base body (8). The chassis plastic component (3) has insulation for the radiation in a radar frequency range between 75 GHz and 85 GHz at least in one radar transparency section (10), the absolute value of said insulation being less than 3 dB in the single run. The result is a chassis plastic component, the use of which for covering a radar-based system is ensured with the least possible restrictions.

Description

Body-plastic component for a motor vehicle and its use

The invention relates to a body-plastic component for a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to a use of such a body-plastic component.

Such body-plastic components are known for example from DE 102004049148 A1.

In motor vehicles radar-based systems are increasingly being used. Depending on the design, these systems measure the distance of the motor vehicle in which they are used from short and / or long-range distances to obstacles in the forward or backward direction. An application of such radar-based systems behind the known body-plastic components is often not possible.

It is therefore an object of the present invention, a body-plastic component of the type mentioned in such a way that its use to cover a radar-based system is guaranteed as fully as possible.

This object is achieved by a body-plastic component having the features specified in claim 1.

According to the invention it was recognized that in the radar frequency range between 75 GHz and 85 GHz, the use of known body-plastic components due to their for this radar frequency range too high insertion loss of the radar radiation, so too high attenuation in an inserted into the radar beam component, was not possible. Instead of the term of insertion loss is often referred to below shortened by a damping. Surprisingly, it was further recognized that it is possible to modify the body-plastic component regardless of a possibly applied to the body paint layer over the known body-plastic components so that the desired low attenuation can be achieved. In this way, it is possible to specify a body-plastic component, which can then be painted with the paint types and color palettes known in automotive technology, in particular with effect paints, without the required low attenuation value of the body plastic component for the radar radiation is exceeded. The body-plastic component can then be used, for example, universally for the currently known coatings, while maintaining such low attenuation at least in the radar transparency portion that the body-plastic component can serve to cover a radar-based system of the type mentioned above. The basic body according to the invention is used in particular as a bumper or as a license plate carrier for the motor vehicle. Depending on whether the radar-based system for which the body plastic component is designed is short-range or long-range, other maximum attenuation limits, also referred to as one-way insertion loss, may be tolerated. For a short-range application, for example for a radar distance measurement in the range of a few m to a maximum of 10 m, a maximum one-way insertion loss of 3 dB is preferred. Even more preferred are maximum one-way insertion loss of 1.5 dB or 1.0 dB. For a long-range application, for example for a radar distance measurement up to 100

or 200 m range, the radar-based system prefers maximum one-way insertion loss of 1.8 dB, 1.0 dB and 0.7 dB. In addition to the maximum one-way insertion loss and an upper limit for a reflection of the bodywork plastic component in the radar frequency range between 75 GHz and 85 GHz is preferred. This reflection should preferably be less than -6 dB, more preferably less than -8 dB. This low reflection prevents, especially in the short-range application of the radar-based system disturbing the signal evaluation by a reflected from the body-plastic component of the radar emitted from a radar transmitter radar. The base body can also be unpainted or used with a foil coating instead of a varnish. In this case, a lacquered and back-injected or even an unpainted film can be used.

Materials according to claim 2 have been proven for the construction of the body. The main body can be produced in particular as an injection-molded component. Here, the mineral or reinforcing filler improve the properties of the body. Even a base made of unreinforced materials is possible. Surprisingly, it was recognized that a low damping according to the invention of the support body of the body-plastic component can be achieved if its wall thickness is maintained in one of the wall thickness ranges specified in claims 3 and 4. Typical wall thicknesses of known body-plastic components lie for example just between the wall thickness ranges according to claims 3 and 4, where an intolerable insertion loss maximum for radar frequencies between 75 GHz and 85 GHz. With regard to its wall thickness, the body-plastic component according to the invention is designed, at least in the radar-transparency section, such that it is not present there for the radar transparency of an unreasonable thickness range. A wall thickness, at least in the radar transparent section, between 1.9 mm and 2.4 mm is preferably suitable for support bodies made of a polycarbonate / polybutylene terephthalate mixture (PC / PBT). A wall thickness, at least in the Radartransparentabschnitt, between 3.1 mm and 3.7 mm is preferably suitable for support body made of elastomer-modified polypropylene (EM PP).

A heating foil according to claim 5 ensures that the radar transparency of the radar transparency portion is not affected by snow crystals, slush or by an ice layer on the radar transparency portion of the body plastic component. The heating foil may be formed as described in DE 102004049148 A1.

Further advantageous heating films represent so-called full-surface heating foils without geometrically defined heating conductor tracks, such as ITO films (indium tin oxide based) or films of nanomaterials. Further advantageous heating foils can be so-called FPC foils (flexible printed circuit), which can be glued on.

According to the invention, it was further recognized that in the case in which a heating foil is present in the radar transparency section, the thickness of the base body changes, in particular reduces, in accordance with the thickness of the heating foil. The wall thickness ranges for the basic body according to claims 6 and 7, which are advantageous for achieving the damping according to the invention, then result. In order to avoid an adaptation of the wall thickness ranges can be used on the body Flammengespritzte Heizleiterbahnen or in the so-called Flamecon method applied heating conductors (for example, copper, silver, gold or any other electrically conductive material). In both cases, the Heizleiterbahnen be applied directly to the body-plastic component (such as bumpers, mesh panels, license plate carrier) and connect firmly with this. The connections to the Heizleiterbahnen can be glued or can be encapsulated (ie, the contacts are, so as not to appear on the visible side, for example, applied to webs). The web width of the Heizleiterbahnen advantageously has a value of less than 1 mm, more preferably from 0.8 mm to 0.5 mm. Since a film carrier for the Heizleiterbahnen deleted, resulting in achieving the damping of the invention advantageous wall thickness ranges without that the strength of the body is significantly changed.

Similarly, the Heizleiterbahnen can be applied to the body-plastic component in a screen printing and / or pad printing process. In this case, conductive pastes may be used which are e.g. Copper, silver, gold or carbon included. The power supply can be realized in this case via solder points, or over bonded copper foils.

To reduce the required heating power of the heating foil in operative connection with the Radarsende- and -empfangseinheit it may be advantageous that behind the heating foil, or the Heizleiterbahnen an additional insulating (advantageously self-adhesive) of foamed polyethylene or polypropylene with a layer thickness in the range of about 1 mm to 5 mm. This advantageously reduces heat losses under extreme cold conditions (heat focusing forward to the outside of the plastic component).

The insulating film can be inexpensively applied to the heating foil in conventional adhesive technology. To further minimize the entry of dirty water or salt water on the Heizfolienoberfläche the arrangement consisting of heating foil and applied insulating foil inside, bordered for example by means of an advantageously circumferentially applied sealing varnish or by means of a sealing paste or by means of a sealing foam or by means of a hot melt adhesive. The insulating film is preferably only with about 0.3 dB in the two-way insertion loss. A wall thickness optimized in the sense of claims 3, 4, 6 and 7 can be realized by a wall thickness realized over the entire body-plastic component or by a wall thickness of the support body or the base body which is partially optimized in particular in the radar transparency portion. Here, the partially optimized wall thickness can be achieved by a corresponding tool design in the production of the body-plastic component or by subsequently applied in particular in the radar transparency portion correction films.

A plastic film according to claim 8 can serve as a correction film to achieve an advantageous for the radar transparency wall thickness range.

A film material according to claim 9 has proven itself for use in such a correction film.

Film thicknesses according to claim 10 ensure a sufficiently fine gradation of a wall thickness change of the support body by the applied plastic film, so that a wall thickness range can be achieved with low damping according to the invention by applying at least one correction film safely. Film thicknesses of 0.125 mm or 0.2 mm have been found to be advantageous in practice.

A surface structure according to claim 11 has been found to improve the radar transparency of the plastic component to be advantageous.

Variants of the body-plastic component according to claims 12 and 13 are already prepared for use as a visible component of a motor vehicle.

A paint according to claim 14 represents a preferred embodiment of a paint, with a low damping according to the invention of the body-plastic component can be achieved. Possible materials for the pigmentation are mica, metal oxides, for example Al ₂ O _3, SiO _2, TiO _2, Fe ₂ O _3, Cr ₂ O _3, or metal particles such as aluminum, indium, silver, the treated accordingly resistant to corrosion in the surface, eg chromatised or silanized, can be adjusted. The effect layer may additionally comprise fillers and binders. Also, two or more such effect layers with different pigmentations are possible for the production of certain color impressions. Layer thicknesses according to claim 15 lead to an advantageously low influence of the coating on the radar transparency of the body-plastic component. In particular, when the pigmentation rather disturbs the passage of the radar radiation used, an effect layer having this pigmentation with a thickness which is not greater than 14 μm, for example, in the case of silver shades, is advantageous. It has been recognized that the pigmentation rather disturbs the passage of the radar radiation used when coarse or medium effect flake pigments are used. A grain size distribution of coarse effect pigment flakes will be defined below. Also defined below is a grain size distribution of fine effect pigment flakes. Medium coarse effect pigment flakes have a size that lies between the fine and coarse effect pigment flakes. Effect pigments that produce a silver tint are usually produced with aluminum particles or flakes. In the case of pigmentations with effect pigment flakes to produce a color impression deviating from a silver shade, even if the pigmentation rather disturbs the passage of the radar radiation used because of the size of the flakes, an effect layer having a thickness having this pigmentation can be used with a thickness, which is greater than 14 microns, for example, with a thickness of 20 microns or 25 microns.

Fine effect pigment flakes according to claim 16 then have an advantageously low influence on the radar transparency when used in the effect layer in low concentration. Fine effect pigment flakes are those which have a particle size distribution in which 90% of the flakes are less than or equal to 31 μm and 50% of the flakes have a particle size of less than or equal to 14 μm. As fine effect pigment flakes and silver dollars can be used, which are more concentrated in terms of their shape and size distribution than other flakes by a certain value, so are uniformly shaped. Fine silver dollars are present when 90% of the flakes are less than or equal to 20 microns and 50% of the flakes have a particle size less than or equal to 12 microns.

Coarse effect pigment flakes according to claim 17 have in relation to the edge length a much larger surface area than fine effect pigment flakes. It has been recognized that an effect layer with such coarse effect pigment flakes does not impair the radar transparency of the bodywork plastic component if the effect layer with a predominant proportion of coarse effect pigment flakes is either not too thick or not the only color layer contributing to the color effect. A construction with at least two effect layers can have a base effect layer and a cover effect layer covering it. The base effect layer with a predominant proportion of fine effect pigment flakes is a basis of the color effect and is well radar-transparent as a layer. The cover effect layer with a predominant proportion of coarse effect pigment flakes can then be made with a smaller thickness, since the color effect of this cover effect layer is only needed as a finish. Preference is given to layer thickness distributions of the base effect layer to the cover effect layer with relative proportions of 70 to 30 to 30 to 70. With a total layer thickness of the two effect layers of not more than 25 μm, the base effect layer can have a thickness of 17.5 μm and the cover effect layer have a thickness of 7.5 microns. The base effect layer can also be made thinner up to a layer thickness distribution with a thickness of the base effect layer of 7.5 μm and a thickness of the cover effect layer of 17.5 μm. The total layer thickness of the two effect layers can be up to 35 Dm. This is especially true for the color white. Also, all intermediate layer thicknesses between these two limits are possible. Coarse effect pigment flakes are those which have a particle size distribution in which 90% of the flakes are less than or equal to 32 μm and 50% of the flakes have a particle size of less than or equal to 20 μm. You can also use rough silver dollars. Coarse silver dollars are present when 90% of the flakes are less than or equal to 32 μm and 50% of the flakes have a grain size of less than or equal to 20 μm.

The advantages of a layer thickness of the cover layer according to claim 18 correspond to those of a layer thickness of the effect layer according to claim 15.

A primer layer according to claim 19, for example, improve the adhesion of the effect layer on the base body. The primer layer, which is a primer, may additionally contain fillers and binders. The primer layer may be free of effect pigment. Optionally, it is also possible to use effect pigments in the primer layer. Here it is preferred to use effect pigments with a predominant proportion of fine effect pigment flakes. The primer layer may be electrically conductive. This can be tolerated in connection with the radar-based system, in particular if the radar-based system has a good tolerance to a reflected beam component. Omission of the primer layer is in many cases even preferred, as this typically reduces the one-way insertion loss of the body plastic part. Depending on the choice of the base body, it may be advantageous that the paint or primer adhesion of the base body is improved by activating the surface (eg by flaming, coronating, plasma pretreatment, laser irradiation, etc.) of the base body.

A primer layer according to claim 20 is advantageously used where an electrical insulation of the base body from the other lacquer layer is required. In addition, an insulating primer layer advantageously influences both the one-way insertion loss and the reflection of the correspondingly equipped body-plastic component in the interesting radar frequency range. When using a non-conductive primer layer and an electrostatic application technique (ESTA) for paint application, a conductive cover layer covering the effect layer is usually used in the form of a conductive clearcoat. In principle, alternatively, a conductive primer layer can also be used where this has no effect on the one-way insertion loss or the reflection of the body-plastic component, which can no longer be tolerated by the radar-based system.

The advantages of a layer thickness of the primer layer according to claim 21 correspond to those of a layer thickness of the effect layer according to claim 15. A primer layer which is less than 10 μm is also possible and even in some applications, especially if the primer layer has effect pigments prefers.

The variants of a dyed body-plastic component according to claims 22 and 23 come depending on the requirements that are placed on the visual color impression of the body-plastic component, advantageously used.

The advantages of using the body-plastic component according to the invention according to claim 24 correspond to those which have already been explained above with reference to the body-plastic component according to the invention. The body-plastic component used according to the invention can have all the features that have already been discussed above.

Embodiments of the invention will be explained in more detail with reference to the drawing. In this show: Fig. 1 shows schematically a section of a front body portion of a

Motor vehicle with a radar sensor with emission examples for a long-range and a short-range operating mode;

FIG. 2 shows, in a view similar to FIG. 1, a further embodiment of a bodywork plastic component of the body region with plastic films applied in a radar transparency section; FIG.

FIG. 3 shows, in a view similar to FIG. 1, a variant of the body-plastic component with a heating foil applied at least in the radar-transparency section;

4 shows in cross-section an enlarged detail of FIG. 1 in the region of a paint applied to a main body of the body-plastic component with a layer structure;

Fig. 5 in a similar to Figure 4 representation of another embodiment of a paint layer structure.

6 shows a diagram which shows an insertion loss of radar radiation in the range between 75 GHz and 85 GHz as a function of a wall thickness of the main body of the body-plastic component;

FIG. 7 shows, in a representation similar to FIG. 6, a wall thickness-dependent attenuation for the radar radiation for different layer constructions of the main body optionally coated with a first effect lacquer; FIG.

FIG. 8 shows, in a representation similar to FIG. 6, a wall thickness-dependent attenuation for the radar radiation for different layer constructions of the main body optionally coated with a second effect lacquer; FIG.

FIG. 9 shows, in a representation similar to FIG. 6, a wall thickness-dependent attenuation for the radar radiation for layer constructions of the main body optionally coated with a third effect lacquer; FIG. 10 shows a diagram which shows a wall thickness-dependent damping of the main body with a first effect varnish for radar radiation of different frequencies;

11 shows a diagram which shows a wall thickness-dependent damping of the main body with a second effect varnish for radar radiation of different frequencies; and

12 shows a diagram which shows a wall thickness-dependent attenuation of the main body with a third effect varnish for radar radiation of different frequencies,

FIG. 13 shows, in a view similar to FIG. 1, a further embodiment of a bodywork plastic component of the body region with heating conductor tracks applied by flame spraying in a radar transparency section.

Fig. 1 shows very schematically an installation of a radar transceiver unit 1 in a front body portion of a motor vehicle. The radar transceiver unit comprises a housing 2, which includes a radar source, a radar detector and a control, supply and evaluation electronics. Facing a front bodywork plastic component 3 of the motor vehicle is a dome-shaped radar window 4, which is also referred to as a dome.

Shown in FIG. 1 by dashed lines are two different Abstrahlcharakte- statistics 5, 6, which are possible in the radar transceiver unit 1. The more concentrated emission characteristic 5 belongs to a long-range operating mode of the unit 1, with which, for example, a distance of the motor vehicle having the unit 1 to a preceding motor vehicle can be determined. The less concentrated, thus more divergent emission characteristic 6 belongs to a kurzreichweitigen operating mode of the radar transceiver unit 1. The kurzreichweitigen mode can be, for example, a motor vehicle closely adjacent obstacle, such as a bollard or a pedestrian recognize. The radar radiation emitted in both modes of operation has a fixed frequency which is, for example, within the frequency band between 75 GHz and 85 GHz. For a short-range application of the radar transceiver unit 1, a radar frequency of 79 GHz can be used. For a long-range application of the radar transceiver unit 1, a radar frequency of 76.5 or 77 GHz can be used.

The body-plastic component 3 is in particular a bumper. Another exemplary embodiment of body-plastic component 3 is a license plate carrier. The body-plastic component 3 has a support body 7 with a base body 8 made of plastic. This may be, for example, one of the plastic materials listed below: PC (polycarbonate), PC / PBT (polycarbonate / polybutylene terephthalate mixture), in particular with a mineral filler, elastomer-modified polypropylene (EM-PP), in particular reinforced with talc, PP / EPDM (polypropylene / ethylene-propylene-diene monomer mixture), ABS (acrylonitrile-butadiene-styrene), ABS / PC (acrylonitrile-butadiene-styrene / polycarbonate blend), ASA (acrylic ester-styrene-acrylonitrile), PA (Polyamide) and its blends, PPO / PA (polypropylene oxide / polyamide blend), PUR (polyurethane), especially in the form of a foam, PCIPET (polycarbonate / polyethylene terephthalate blend) or PBT (polybutylene terephthalate). A combination of these plastic materials is possible to build the body 8. The base body 8 can be produced as an injection-molded component. As minerals, talc, chalk, wollastonite, mica, glass beads and fibrous fillers can be used regardless of the base material.

In the embodiment of Fig. 1, the support body 7 and the base body 8 are identical. On the base body 8, a paint 9 is applied.

The body-plastic component 3, so the painted support body 7, for the radar radiation with the emission characteristics 5, 6 an insertion loss whose absolute value is less than 3 dB in a single pass, preferably less than 1, 8 dB in a single pass, more preferably is less than 1.5 dB in single pass, more preferably less than 1.0 dB in single pass, and more preferably less than 0.7 dB in single pass.

After passing through the body-plastic component 3, the radar radiated through is therefore present at a power which amounts to at least 50% of the power incident on the bodywork plastic component 3. The damping formula applies here:

a = 10 - log (P, / P ₂ ) dB

a hereby marks the damping. P2 designates the power of the radar radiation transmitted through the bodywork plastic component 3 and P1 the power of the radar radiation impinging on the bodywork plastic component 3.

An attenuation of 3 dB in a single pass represents the maximum allowable for the operation of the radar transceiver unit 1 attenuation.

The reflectivity of the body-plastic component 3 also has an influence on the function of the radar transceiver unit 1. The reflection value r is determined by the following formula:

T = IO - IOg (RZP ₁ )

r denotes the power of the radar radiation reflected by the body-plastic component 3.

The body plastic component 3 has a reflection value r smaller than -6 dB, and preferably smaller than -8 dB.

The radar transceiver unit 1 has a certain signal / noise ratio, which can be determined by a measurement. On the basis of this signal / noise ratio can be determined how large a measurement signal must be, so that it can be distinguished with the radar transceiver unit 1 of a noise signal. The measurement signal is affected by a number of influences on its way when performing a distance measurement. These include the power losses during passage through the body-plastic component 3 and other losses, the radar radiation along its airway, especially under certain environmental conditions such as rain or fog experiences. Further losses of the measuring radar radiation result for example from the deviating from the ideal value reflectivity of the object to be measured. Finally, the radar measurement signal arriving at the receiver of the radar transceiver unit 1 must be clearly distinguishable from interfering signals reflected at the body plastic component 3.

The support body 7, in the case of the embodiment according to FIG. 1, ie the base body 8, has a wall thickness d between at least in a radar transparency section 10 in which the radar radiation impinges on the wall of the body plastic component 3 facing the radar transceiver unit 1 1.9 mm and 2.4 mm. In an alternative embodiment, the support body 7 in the radar transparency portion 10 have a wall thickness between 3.1 mm and 3.7 mm.

As shown in the diagram of FIG. 6, the damping of the support body 7 in each case has a minimum in these thickness ranges, so it is particularly low there. FIG. 6 shows the result of a one-way insertion loss measurement for support bodies 7 with different wall thicknesses in the radar transparency area 10 for radar radiation at a measurement frequency of 76.5 GHz. In fact, one-way insertion loss was measured with the attenuation values doubled for illustration in FIG. With a wall thickness of about 2.2 mm, an attenuation a of less than 0.5 dB results. At a wall thickness of the support body 7 of about 3.2 mm, the attenuation a is just above 0.5 dB.

4 and 5 show two alternative embodiments for a layer structure of the paint. 9

In the embodiment according to FIG. 4, the lacquer initially has a primer layer 11 applied to the base body 8. The primer layer 11 is not electrically conductive and in the dry state has a layer thickness between 10 μm and 20 μm. On this an effect layer 12 is applied, which includes a pigmentation 13, which is shown schematically in FIG. The pigmentation 13 of the effect layer 12 according to FIG. 4 is a pigmentation of fine effect pigment flakes. Fine effect pigment flakes are those which have a particle size distribution in which 90% of the flakes are less than or equal to 31 μm and 50% of the flakes have a particle size of less than or equal to 14 μm. The fine effect pigment flakes have a typical diameter of 10 μm. Also, much smaller particle sizes of the pigmentation 13 are possible, for example, particles with a size below 1 micron, for example, with a size of 0.2 microns. The effect layer 12 has in addition to the pigmentation 13 still fillers and binders. The effect layer 12 in the dry state has a layer thickness of between 7 μm and 35 μm, in particular between 10 μm and 30 μm, in particular in the region of 15 μm. The effect layer 12 is covered to the visible side of the body-plastic component 3 by a cover layer 14, which may be in particular a clearcoat. The cover layer 14 has a layer thickness of between 25 μm and 40 μm in the dry state.

In the case of the paint variant according to FIG. 5, the paint 9 has two effect layers 15, 16 which are arranged one above the other between the primer layer 11 and the cover layer 14. The effect layer 15 applied directly to the primer layer 11 has a predominant proportion of fine effect pigment flakes in the pigmentation 13, and thus, as far as the pigmentation is concerned, it is structured like the effect layer 12 of the embodiment according to FIG. 4. The effect layer between the effect layer 15 and coarse effect pigment flakes are those which have a particle size distribution at which 90% of the flakes are less than or equal to 32 μm and 50% of the flakes have a particle size less than or equal to 20 microns. The coarse effect pigment flakes have a diameter with a typical dimension of 100 μm. The coarse effect pigment flakes of pigmentation 17 are shaped in particular as so-called "silver dollars", meaning that the silver dollars have a lower ratio of flake edge length and flake surface than the fine effect pigment flakes.

The flakes are approximately disc-shaped and are aligned during the application of the varnish 9, in particular when applying the effect layers 12 or 15, 16.

It is advantageous for the radar transparency of the varnish 9 if the dielectric constant of the varnish layer as a whole is not greater than 20 at a radar frequency of 79 GHz. Under certain conditions basecoats can also be used for the varnish 9 with a considerably larger number of electrolytes.

Paints, in particular effect layers, which are used as lacquer 9 are known, for example, from DE 102004051104 A1, DE 102004049734 A1, DE 102004049203 A1, DE 102004045352 A1, DE 102004052544 A1, DE 102005001997 A1, DE 102004042012 A1, DE 102004039554 A1, DE 102004035769 A1, DE 69723347 T2, DE 19915153 A1 and DE 19842134 A1. Fig. 2 shows another embodiment of a supporting body 7 of the body-plastic component 3. Components which correspond to those which have already been explained above with reference to the figures bear the same reference numerals and will not be discussed again in detail.

In the embodiment of the support body 7 according to FIG. 2, a plastic film 18 is applied to the base body 8 in the radar transparency section 10 on the side facing the radar transmitting / receiving unit 1. The plastic film 18 is made of PET.

Other materials for the plastic film 18 are possible, for example PP (polypropylene), PE (polyethylene), PC (polycarbonate), PMMA (polymethyl methacrylate), ABS (acrylonitrile-butadiene-styrene). The plastic film 18 may be formed as a single-layer film or as a coextrusion film. The bonding of the plastic film 18 to the base body 8 is such that penetration of water between the base body 8 and the plastic film 18 is prevented. The plastic film 18 can in principle be designed so that it also has the function of a heating foil, which will be described below.

The plastic film 18 has a film thickness of 0.2 mm. Other film thicknesses, for example in the range between 0.1 mm and 0.5 mm, e.g. a film thickness of

0,125 mm, are possible. Optionally, on the plastic film 18 in the radar transparency portion 10 still another plastic film 18, as indicated by dashed lines in Fig. 2, or it can also be several more plastic films 18 are applied. The thickness of the at least one plastic film 18 therefore contributes to the wall thickness d of the base body in each case. With the plastic film 18 or the plastic films 18, a strength adjustment of the base body 8 and thus the entire support body 7 in Radartransparenzabschnitt 10 are brought about, so that one of the wall thickness ranges is achieved, in which the damping a of the two in connection with FIG explained minima has. In this way, the at least one plastic film 18 serves as a correction film for optimizing a lower damping of the body-plastic component 3 for the radar transceiver unit 1. On the radar transmitting / receiving unit 1 side facing in the case of the embodiment of FIG. 1, the base body 8 or in the case of the embodiment of FIG. 2, the plastic film 18 at least in the radar transparency portion 10, a surface structure to reduce the attenuation of the radar during Entrance into the support body 7 in the Hinlauf and the exit from the support body 7 in the return have. Since this surface structure is applied on the side facing away from the visible side of the body-plastic component 3, the overall visual impression of the body-plastic component 3 is not changed from the visible side by the surface structure. This surface structure on the support body 7 and / or on the plastic film 18 has a typical depth dimension, which is on the order of 1/10 of the wavelength of the radar radiation to be applied. The surface structure may have pattern structures with a typical depth of 0.2 mm, in particular with a maximum depth of 0.4 mm. By means of these pattern structures, a beam deflection, in particular of at least 7 °, can be effected. The beam deflection advantageously causes only insignificant back reflection of the emitted radar steel. Otherwise, the sensor would be outshined by the signal of this back reflection and thus become virtually blind to the evaluation of the useful signal reflected back by an object.

3 shows a further embodiment of a supporting body 7 of the body-plastic component 3. Components which correspond to those which have already been explained above with reference to the figures have the same reference numerals and will not be discussed again in detail.

On the side facing the radar transceiver unit 1, the main body 8 carries a heating foil 19 glued onto it. The heating foil 19 has a foil thickness of between 0.1 and 0.3 mm. The heating foil 19 may in particular be constructed as described in DE 102004049148 A1.

The heating foil 19 is applied to the base body 8 at least in the region of the radar transparency cut 10. In the embodiment of FIG. 3, the heating foil 19 goes beyond the radar transparency portion 10. The heating foil 19 tempers the body-plastic component 3 at least in the radar transparency portion 10 such that during operation of the motor vehicle equipped with the bodywork plastic component 3, at least the radar transparency portion 10 remains ice-free even in cold weather conditions. Therefore, during operation of the motor vehicle, snow or ice can not impair the operation of the radar transceiver unit 1 due to additional absorption or scattering of radar radiation by snow crystals or through an ice layer in the area of the radar transparency section 10. Another advantage lies in the fact that even moisture deposits can be evaporated, which otherwise also contribute to an undesired absorption and / or scattering of the radar radiation.

By the applied heating foil 19, the strength of the supporting body 7 increases overall. The wall thickness ranges of the base body 8 in the embodiment according to FIG. 3, in which the damping a of the body-plastic component 3 is minimized, therefore shift in relation to the illustration according to FIG. 6 towards smaller wall thicknesses of the base body 8 first minimum, which is achieved without heating foil 19 in the range of 1, 9 mm ≤ d <2.4 mm, is achieved with the heating foil 19 in a range between 1.8 mm and 2.2 mm. The further minimum of the damping a, which is achieved without a heating foil 19 in a range of 3.1 mm ≦ d ≦ 3.7 mm, becomes with the heating foil 19 in a range of the wall thickness d of the main body 8 between 3.0 mm and 3 , 4 mm reached. By means of the heating foil 19, it can be ensured, in particular, that practically no impairment of the radar transparency of the bodywork plastic component 3 by snow crystals or an ice layer is present when used in a motor vehicle driving at a speed of 120 km / h for two hours or more during snowfall.

An unspecified embodiment of the support body 7 shown in Figure 3, in addition to the heating foil 19 on the visible side, a 2-layer or 3-layer coating 9 on. The heating foil 19 may have a PET carrier layer and an adhesive layer whose thicknesses are in each case in the range from 100 μm to 200 μm. Due to the PET carrier, the adhesive layer and the paint layer, the strength of the support body 7 increases overall. According to the invention, the wall thickness d of the main body 8 in the case of the used material EM-PP is between 3.1 mm and 3.3 mm, or for the material PC / PBT between 1.8 mm and 2.1 mm.

FIG. 7 shows a two-way insertion loss a in decibels over the wall thickness d of the base body 8. The base body 8 is irradiated with the radar radiation at an angle of incidence in the range of approximately 14 ° to the normal. This angle of incidence corresponds to typical installation conditions of the radar transceiver unit 1 relative to the body plastic component 3 in current vehicle designs. 7, a damping curve for the pure, unpainted main body 8 is shown in a solid line.

Shown in dashed lines in FIG. 7 is a damping curve for the main body 8 with the respective wall thickness d and an additionally applied lacquer 9 with a two-layer structure. In this case, therefore, the lacquer 9 has exactly one effect layer 12 and the cover layer 14, wherein no primer layer 11 is present between the effect layer 12 and the base body 8.

In dashed lines in FIG. 7, a damping curve is plotted as a function of the layer thickness of the base body 8, in which a coating 9 is applied to the base body 8 as a three-layer structure. This three-layer structure differs from the two-layer structure of the dashed attenuation curve in FIG. 7 only by an additional Liehe primer layer 11 between the base body 8 and the effect layer 12. The dot-dashed attenuation curve "three-layer structure" is compared to the dashed attenuation curve "two Layer structure "shifted by about 1.5 dB towards higher attenuation.

Regardless of the layer structure, it remains the case that with wall thicknesses d of the base body 8 of 2.2 mm on the one hand and from about 3.2 mm on the other hand a small and tolerable for the use of the radar transceiver unit 1 attenuation a is present.

The varnish variant of FIG. 7 is a varnish 9 having an effect layer 12 with a silver pigmentation 13 with a first size and quantity distribution of the flakes, in which predominantly finer flakes are used. The typical silver pigmentation 13 takes place with flakes in the form of aluminum particles.

Fig. 8 shows in a similar to Fig. 7 representation with the measurement setup, which was also used in FIG. 7, recorded damping curves on the one hand for the unpainted base 8 (solid) and on the other hand for a two-layer structure (dashed) and for a three-layer structure (dash-dotted) of paint applied to this 9. The difference between the paints applied in the embodiment according to FIG. 7 and in the embodiment according to FIG. 8 lies in the formulation of the effect layer 12. This is in the embodiment, which is carried out to the damping characteristic of FIG. 8 with compared to the embodiment of FIG. 7 a pigmentation 17 with coarser flakes. Also in the embodiment of Fig. 8 is a silver effect layer.

The base body 8, on which the damping measurements of FIGS. 7 and 8 were carried out, is made of elastomer-modified polypropylene with a 10% talcum reinforcement (EM PP TV 10). Also, a proportion of talcum reinforcement of 20% is possible (TV 20).

The attenuation measurements of FIGS. 7 and 8 were performed at a radar frequency of 76.5 GHz.

9 shows in a further diagram two damping curves as a function of the wall thickness d of the main body 8. The latter is made of the same material as the basic body 8 on which the damping measurements according to FIGS. 7 and 8 were carried out. In FIG. 9, a one-way damping a is applied over the wall thickness d. Dash-dotted a damping curve for the unpainted base 8 is shown.

The radar measurement frequency is 76.5 GHz in the measurement of FIG. 9.

The damping behavior of the unpainted base body 8 in the measurement according to FIG. 9 corresponds to that in the measurements according to FIGS. 7 and 8.

Dashed lines in FIG. 9 a damping curve is shown, which shows the wall thickness-dependent damping behavior of a painted base body 8. The main body 8 is provided with a varnish 9 having a layer structure according to FIG. 4. As effect layer 12, a layer with blue pigmentation is applied. This results in the painted body a wall thickness-dependent damping curve with a minimum at d = 2.3 mm and a significant drop in the attenuation a for wall thickness d above 3.1 mm.

10 shows in a further diagram a frequency dependence of the wall thickness-dependent one-way damping characteristic for a base body 8, on which a lacquer 9 with a three-layer structure corresponding to that according to FIG. 4 is plotted. Shown are wall thickness-dependent one-way attenuation curves for radar frequencies 76.5 GHz, 77 GHz, 79 GHz and 81 GHz. With increasing radar frequency results in a shift of the damping curve towards slightly smaller wall thicknesses. The curves and also the absolute losses a are essentially retained. Minimal attenuation thus results in the measured frequency range substantially independent of frequency at the same wall thicknesses.

The effect layer 12 of the varnish 9, with which the attenuation measurements shown in FIG. 10 were carried out, has a silver-colored pigmentation 13.

In the damping curves discussed below, components of the bodywork plastic component 3, which have already been explained above, are again designated by the same reference numerals. These components are explained in detail only where they differ from what has been previously discussed.

FIG. 11 shows, in a representation similar to FIG. 10, the radar frequency dependence of a one-way attenuation a dependent on the wall thickness d of the main body 8 for a three-layered lacquer 9 according to FIG. 9 and an effect layer 12 with a beige pigmentation 13. Qualitative 11 corresponds to the behavior of the damping curves in FIG. 10. The displacement of the damping curves for increasing radar frequencies toward smaller wall thicknesses d of the main body 8 is not as pronounced in the measurement of FIG. 11 as in that of FIG. 10.

FIG. 12 shows, in a representation similar to FIG. 10, the radar frequency dependence of a one-way attenuation a dependent on the wall thickness d of the main body 8 for a lacquer 9 with two-layer structure corresponding to the dashed measuring curve of FIGS. 7 and 8 and an effect layer 12 a silver-colored pigmentation 13, in which case the primary layer 11 has been omitted. Qualitatively, the behavior of the damping curves in FIG. 12 corresponds to that of FIG. 10. The displacement of the damping curves for increasing radar frequencies toward smaller wall thicknesses d of the main body 8 is not as pronounced in the measurement of FIG. 12 as in that of FIG , but somewhat stronger than in the measurement of FIG. 11.

FIG. 13 shows, in a representation similar to FIG. 1, very schematically an installation of a radar transceiver unit 1 in a front body region of a motor vehicle. The shown body-plastic component 3 is in particular a bumper. The body-plastic component 3 has a base support body 21 with a base body 8 made of plastic. In the embodiment according to FIG. 13, the base support body 21 has a wall thickness b and the base body 8 has a wall thickness d. The wall thickness b of the base support body lies just between the wall thickness ranges according to claims 3 and 4, where an intolerable insertion loss maximum for radar frequencies lies between 75 GHz and 85 GHz. Due to this, the body-plastic component 3 according to the invention is designed, with regard to its wall thickness d, at least in the radar transparency portion 10 such that this strength range unfavorable for the radar transparency is not present there. In this case, the wall thickness in the radar-transparent portion 10 is made stronger. According to the invention, of course, the reverse case is conceivable that the wall thickness d is not larger, but smaller than the wall thickness b is executed. In addition, the base body has heat conductor tracks 20 applied to the side facing the radar transceiver unit 1 by means of a flame spraying method. The heating conductor tracks 20 are fixedly connected to the main body 8 at substantially equidistant distances from one another. The web width of the Heizleiterbahnen advantageously has a value of 0.7 mm. On the base body 8, a paint 9 is applied. The wall thickness d of the base body 8 for the material used EMPP in this case is in a range between 2.0 mm and 2.4 mm, and between 3.2 mm and 3.5 mm.

In a non-illustrated embodiment of the body-plastic component 3 shown in Figure 13 with applied in the flame-spraying Heizleiterbahnen 20 no paint is applied to the base body 8. In this case, the wall thickness d of the main body 8 is between 3.4 mm and 3.7 mm for the material used, EM PP. For the material PC / PBT, the wall thickness d of the main body 8 is without a coating application in a range between 2.1 mm and 2.3 mm, and between 3.1 mm and 3.5 mm.

- Claims -

Claims

claims

1. body plastic component (3) for a motor vehicle

- With a support body (7) with a base body (8) made of plastic, characterized in that the body plastic component (3) for radiation in a radar frequency range between 75 GHz and 85 GHz at least in a radar transparency portion (10) has an attenuation whose absolute value is less than 3 dB in single pass.

2. Plastic body component according to claim 1, characterized in that the base body (8) is made of at least one of the following materials: - PC (polycarbonate),

PC / PBT (polycarbonate / polybutylene terephthalate mixture), in particular with a mineral filler,

- EM PP (elastomer-modified polypropylene), in particular talc-reinforced,

PP / EPDM (polypropylene / ethylene-propylene-diene monomer mixture), ABS (acrylonitrile-butadiene-styrene),

ABS / PC (acrylonitrile-butadiene-styrene / polycarbonate blend),

- ASA (acrylic ester-styrene-acrylonitrile),

PA (polyamide) and its blends,

PPO / PA (polypropylene oxide / polyamide mixture), PUR (polyurethane), in particular in the form of a foam,

PC / PET (polycarbonate / polyethylene terephthalate mixture),

- or PBT (polybutylene terephthalate).

3. Body-plastic component according to claim 1 or 2, characterized in that the supporting body (7) at least in a radar transparency portion (10) has a wall thickness between 1, 9 mm and 2.4 mm.

4. Body plastic component according to claim 1 or 2, characterized in that the supporting body (7) at least in a radar transparency portion (10) has a wall thickness between 3.1 mm and 3.7 mm.

5. Body-plastic component according to one of claims 1 to 4, characterized in that the supporting body (7) on a side facing away from the paint (9) side of the base body (8) at least in the region of Radartransparenzabschnitts (10) has a heating foil (19) ,

6. body plastic component according to claim 5, characterized in that the base body (8) at least in a radar transparency portion (10) has a wall thickness between 1, 8 mm and 2.2 mm.

7. body plastic component according to claim 5, characterized in that the

Base body (8) at least in a Radartransparenzabschnitt (10) has a wall thickness between 3.0 mm and 3.4 mm.

8. Body-plastic component according to one of claims 1 to 7, characterized marked, that the base body (8) at least in the Radartransparenzabschnitt (10) has a multilayer structure with a base body and at least one plastic film applied thereto (18).

9. body plastic component according to claim 8, characterized in that the plastic film (18) made of PET (polyethylene terephthalate) is made.

10. Body-plastic component according to claim 8 or 9, characterized in that the plastic film (18) has a thickness in the range between 0.1 and 0.5 mm, in particular a thickness of 0.125 mm.

11. Body-plastic component according to one of claims 1 to 10, characterized in that the base body (8) and / or the plastic film (18) has a surface structure.

12. Body-plastic component according to one of claims 1 to 11, characterized in that the base body (8) is colored at least on the face side.

13. Body-plastic component according to claim 12, characterized in that on the

Base body (8) a paint (9) is applied.

14. Bodywork plastic component according to claim 13, characterized in that the lacquer (9) comprises:

at least one effect layer (12, 15, 16) having at least one pigmentation (13, 13, 17), a cover layer (14) covering the effect layer (12, 15, 16) to the outside.

15. Body-plastic component according to claim 14, characterized in that the at least one effect layer (12; 15, 16) has a layer thickness of between 7 μm and 35 μm.

16. Body-plastic component according to claim 14 or 15, characterized by a predominant proportion of fine effect pigment flakes in the pigmentation (13).

17. Body-plastic component according to claim 14 or 15, characterized by a lacquer having at least two effect layers (15, 16), wherein

a base effect layer (15) comprises a predominant proportion of fine effect pigment flakes in the pigmentation (13),

a cover effect layer (16) has a predominant proportion of coarse effect pigment flakes in the pigmentation (17).

18. Body-plastic component according to one of claims 14 to 17, characterized in that the cover layer (14) has a layer thickness between 25 microns and 40 microns.

19. Bodywork plastic component according to one of claims 14 to 18, characterized in that the paint (9) has a primer layer (11) which is arranged between the effect layer (12; 15, 16) and the base body (8).

20. Body-plastic component according to claim 19, characterized in that the primer layer (11) is not electrically conductive.

21. Body-plastic component according to claim 19 or 20, characterized in that the primer layer (11) has a layer thickness between 10 .mu.m and 20 .mu.m.

22. Body-plastic component according to claim 12, characterized in that the base body (8) has a film coating on the visible side.

23. Body-plastic component according to claim 12, characterized in that a basic body (8) forming plastic starting material is colored.

24. Use of a body-plastic component (3) according to one of claims 1 to 23 for a motor vehicle

- As a visible side cover for a radar transceiver unit (1) with an operating frequency between 75 GHz and 85 GHz.